Most notebook computers include a base unit which houses the processor and keyboard of the computer. A top cover which houses a display screen is pivotably secured to the base unit. Low voltage signals for controlling the display screen are provided from the base unit to the display screen by a thin planar flex circuit extending therebetween. The portion of the planar surface of the flex circuit which crosses the hinge axis of the notebook computer actively bends when the top cover opens or closes. The flex circuit has a very thin cross section and is made of material flexible enough to allow the flex circuit to withstand tens of thousands of bending cycles without breaking.
The display screen is commonly backlit to improve viewing. The backlighting is typically powered by a high voltage inverter located within the top cover adjacent to the display screen. The high voltage inverter is enclosed within the top cover because the wires required for carrying high voltage power (about 1500 volts) have a much thicker cross section than a flex circuit making the high voltage wires less flexible and unable to withstand repeated bending cycles. Housing the inverter in the base unit would require the high voltage wires to extend across the hinge axis from the base unit to the display screen, subjecting the high voltage wires to breakage under the repeated bending and exposing the user to the possibility of 1500 volts of high voltage electrical shock.
A drawback of positioning the inverter in the top cover adjacent to the display screen is that the display screen must be smaller than the top cover by at least an amount equal to the width of the inverter. The display screen can be made larger, by locating the inverter behind the display screen. However, this would increase the thickness of the top cover in order to accommodate the inverter, and would in turn increase the overall thickness of the notebook computer.
The present invention is directed to a high voltage electrical connection between a base unit and a panel display in a portable computer wherein the base unit and the panel display are pivotably secured to each other about a hinge axis. The electrical connection includes a flexible high voltage electrical conductor extending from the base unit to the panel display. A portion of the electrical conductor extends along the hinge axis such that pivoting of the panel display relative to the base unit causes said portion of the flexible conductor to twist about the hinge axis rather than actively bend. Twisting a length of flexible conductor about its longitudinal axis exerts less stress on the flexible conductor than if the flexible conductor is repeatedly bent across its longitudinal axis.
In preferred embodiments, the flexible electrical conductor includes two insulated copper braided wires positioned longitudinally adjacent to each other. A sleeve surrounds a portion of the flexible conductor. The sleeve is made of a braided material capable of being shrink fitted over the flexible conductor and prevents wear of the flexible conductor due to twisting of the flexible conductor against components of the computer. Each wire preferably includes 19 twisted tinned annealed copper wire strands about 0.127 mm in diameter which are covered by a polymeric insulation jacket.
The present invention provides an electrical connection which allows the high voltage inverter of a notebook computer to be located in the base unit while at the same time, eliminating the possibility of conductor breakage and high voltage electrical shock to the user. As a result, the size of the display screen can be maximized without increasing the dimensions of the top cover.